In the field of soft robotics, researchers want to mimic the movement of soft bodies found in nature. Soft robots have the unique advantage to be able to adapt to the shape of the object they are touching and are thus safer while working in human environments. It is however
still difficult to measure the position of such a soft body accurately using internal sensors. The significant development in 3D printing technology has made it possible to print soft robots with embedded sensors.
This work shows the design, fabrication and characterisation of a 3D printed pneumatic soft robotic actuator with embedded strain gauges to determine the bending angle of the actuator. The actuator and strain gauges have been printed in one go using a multi-material FDM printer. The actuator contains two strain gauges such that a differential measurement can be performed.
The fabricated actuator is able to bend more than 180° and can apply a force of around 3 N for 0.3 MPa. The differential signal of the embedded strain sensors shows an almost linear relation to the bending angle, while the response of each individual sensor is non-linear due to the nature of the strain gauge material. The proposed model of the actuator is based on the Euler Bernoulli beam theory. The model is however limited by the large deflections of the actuator.